all the man pages and no duplicates...

On my system, it would seem build world includes cat and html
versions of man pages in addition to the nroff files.
With the default man.conf, I get 4 files for "man -a termcap" (the
nroff and cat files for each of termcap(3) and termcap(5)).
I'd like to configure man to respect -a but not bring up duplicate
manuals. After a few attempts in the past I tried it again today
by purging all the "man" directories of the _subdir section of
man.conf. That works great accept some local packages have no cat
equivalant to the nroff files, there may well be packages with cat
files but no nroff too.
So it seems the best fix is to just not produce nroff/cat
duplicate manuals! Is there some way I can configure to do just
one or the other at build world time and will build.sh help me
purge existing duplicate manuals from my install?
-geo